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2007-10-17 15:56:15 · 7 answers · asked by Anonymous in Science & Mathematics ➔ Mathematics
5
2007-10-17 15:59:23 · answer #1 · answered by Lordzero 3 · 0⤊ 0⤋
Congratulations on posting a diagram; this is ingenious.
We can observe several facts about the diagram.
SInce 2 angles are given in terms of x,
& we know that all 3 angles sum to 180.
The angle RST subtracted from 180 leaves 125.
Therefore: x^2 + 20x + (180-125) = 180
So: x^2 + 20x -125 = 0 (a quadratic equation)
Factoring as a binomial:
(x - 5)(x + 25) = 0
Either: x - 5 = 0, so x = 5
Or: x + 25 = 0, so x = -25
Which is the third choice given.
2007-10-17 23:09:49 · answer #2 · answered by Robert S 7 · 0⤊ 0⤋
x = 5
2007-10-17 22:59:35 · answer #3 · answered by p_nutters234 2 · 0⤊ 0⤋
3 sided polynomials will have angles that equal up to 180 degrees.
55 + 100 + 25 = 180 degrees
The answer is 5.
All you have to do is plug in the numbers given for each x.
2007-10-17 23:05:47 · answer #4 · answered by Felicity 2 · 0⤊ 0⤋
Angle RST = 180 - 125 = 55
55 + x^2 +20x = 180
x^2 + 20x -125 = 0
Solve this equation using cross multiplication method and you get x= -25 or 5.
How -25 is rejected because an angle CANNOT BE NEGATIVE.
Hence, the answer is 5.
(:
2007-10-17 23:02:56 · answer #5 · answered by Anonymous · 0⤊ 0⤋
angle RST = 180-125 = 55
the sum of the interior angles = 180, so
x^2+20x+55 = 180
x^2+20x+100 = 225
(x+10)^2 = 225
x+10 = 15
x = 5
2007-10-17 23:03:30 · answer #6 · answered by Kaila G 3 · 0⤊ 0⤋
180-125 = 55
ok angles of triangle = 180 degrees
x^2 + 20x + 55 = 180
x^2 =20x -125 = 0
(x-5)(x+20) = 0
x = 5 and -20
x cannot be negative
therefore x = 5
2007-10-17 23:01:35 · answer #7 · answered by science_guy 5 · 0⤊ 0⤋